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the latest 48 hours of photon data

The first plot below reflects the full-disc solar flux in the
passband 1 to 500 Angstroms (0.1 to 50 nm). The detector is much more
efficient at the shorter wavelengths, effectively measuring the soft
X-ray output of the sun. Two-minute averages are plotted for the last
48 hours. A quiet-time background of 95% of the minimum rate observed
during that 48 hours is subtracted from the data set. Although this SEM
channel has a passband larger than the 1 to 8 Angstrom range that is
traditionally used to classify solar X-ray
events, an approximate correspondence can be made. At a SEM value
of 10**5 (above which saturation occurs), the equivalent X-ray class is
typically within a factor of 2 of an X1 event; i.e., 10**5 ==> M5 to X2.
Similarly, 10**4 ==> C5 to M2. This variable mapping is a product of
different spectra in different X-ray events, and is explored
here

In the second plot is the same quantity, this time for the most recent
4 hours and using the maximum time resolution of 15 seconds.

In the third plot, the bottom panel ("ch2") is again the
1 to 500 Angstrom SEM channel, but
without any background subtraction. The top panel ("ch4") is the first-order SEM
channel with a passband of 304 +- 40 Angstroms. This channel responds primarily
to the very strong Helium 304 line, but is also sensitive to some 'hotter' lines
(i.e., lines enhanced during solar events) in its passband, and can also be
sensitive to background produced by energetic flare particles. For a rough
indicator of the current flare background, see our PM flare plot. Other near-real time
flare monitors are available from ACE/SIS
and Soho/ERNE.

SEM ch2 data ending at
1735 GMT
on Mar 3, 2015

Latest 4 hours of SEM ch2 data ending at
1735 GMT
on Mar 3, 2015

Latest 14 days of SEM ch2, ch4 data ending at
2328 GMT
on Mar 2, 2015

The SEM home page
has a description of the SEM instrument and
calibrated data.
SEM is part of the CELIAS
instrument package on the SOHO
spacecraft. The SEM was designed and constructed by
USC (Darrell Judge, Don
McMullin, Howard Ogawa and colleagues), and is integrated into the
CELIAS/STOF sensor (M.
Hilchenbach, Lead Co-I). D. Hovestadt and E. Moebius were instrumental in
getting the SEM added to the SOHO instrument payload. The data processing and
presentation on this web page are courtesy the
CELIAS/MTOF crew at U of Md.